(1) Field of the Invention
The present invention relates to the establishment of fluid tight seals and particularly the sealing of pipe joints. More specifically, this invention is directed to a sealing ring assembly comprising a gasket ring and a cooperating locking ring. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
(2) Description of the Prior Art
While not limited thereto in its utility, the present invention is particularly well suited for use in the establishment of a fluid tight seal, particularly a liquid seal, for pipe plug joints between an outer conduit element, hereinafter referred to as a "socket", and an inner conduit element which is inserted into the "socket" and which will hereinafter be referred to as the "pointed tip" or "tip". Sealing or gasket rings intended for prefitting in sockets, for example sockets at the joint between serially connectd concrete pipes, are customarily of one or two types. The sealing rings of the first type are known as "roll rings" which are not firmly fastened to the socket. The sealing rings of the second type are known generally as lip gasket rings and are clamped against axial displacement upon insertion of the pointed tip into the socket. A "lip gasket ring" is a sealing element wherein the pipe joint is sealed by means of at least one sealing lip which contacts the conduit tip which is inserted into the socket. The present invention relates to gasket rings of the "lip" type which are fixed in the socket against axial movement.
Gasket or sealing systems of the type with which the present invention is concerned are predominently used to seal the joints between conduit sections wherein the conduits are comprised of mineral materials such as calcined clay, concrete or asbestos cement. When used in the environment of a conduit comprised of a mineral material, the sealing lips of the gasket ring must retain a high degree of mobility while the gasket ring as a whole should not be axially movable. Additionally, because of the manufacturing tolerances inherent in the manufacture of pipes of mineral materials, the gasket systems, and particularly the sealing ring itself, must have the capability of establishing a seal over a relatively wide range of spaces between the tip and socket of the adjacent pipes.
Prior gasket ring systems suitable for use with pipes comprised of mineral materials comprise three functional elements: (1) a gasket ring or ring-shaped sealing lip, (2) a ring-shaped anchoring device, and (3) a ring-shaped intermediate flange which connects the gasket ring and anchoring device. For anchoring a gasket ring to the socket at the end of a conduit section, three techniques have been widely used in the prior art. These techniques include casting, cementing and clamping or locking. The casting and cementing techniques have obvious disadvantages; and the present invention relates to a gasket ring system including a clamping or locking member which provides the axial fixation of the gasket or sealing ring in the socket. More particularly, the present invention pertains to that type of joint seal assembly wherein a gasket ring is fixed by a locking ring in an annular groove formed in the wall of the socket. In accordance with the prior art, the locking rings employed in this type of sealing ring assembly consist of open, spring washers which are pre-stressed radially outwardly and have a circular or flat rectangular cross-section.
Further considering the prior art, it is known to employ spring-lock washers with flat rectangualr surface for immobilizing a gasket ring. Such spring type lock-washers are not suitable for holding rubbery elastic gasket rings in pipes comprised of mineral materials with sufficient firmness. Thus, in practice the gasket ring is not held with sufficient force at the upper limits of the tolerance range while warping of the locking ring and/or of the gasket ring will occur at the lower limits of the tolerance range. Bearing in mind that in many applications, for example in sewer technology, the gasket assembly must be capable of maintaining a leak tight seal for as much as twenty years, it may be understood why locking rings of the open, spring washer type have not been accepted.
The task of achieving a problem-free axial fixation of a gasket ring in pipe plug joints with large diameter tolerance ranges is particularly prevalent in cases where the gasket rings are of the type which have four sealing lips arranged, when the sealing ring is viewed in cross section, in either essentially cross-shaped or X-shaped pattern. Gasket rings having four sealing lips have been developed to correspond to waste water regulations which require integrity of the joint against both internal pressure and external pressure. Considering the harsh conditions to which the gasket ring assembly may be subjected, it is essential that the gasket rings be capable of unhindered pivoting or twisting through their principal radial plane. Thus, the gasket rings require a high degree of mobility and must nevertheless be fixed in position whereby the gasket ring assembly is characterized by axial stability. The prior art has not previously solved the problem of providing adequate mobility or flexibility combined with axial stability.